This document discusses various mortgage calculations and concepts. It begins with an example comparing the present value of receiving $1,000 in 5 years versus $2,000 in 10 years at different discount rates. It then covers key characteristics of mortgages including payment amounts, loan balance, lender yield, and present value of debt. Specific mortgage types like interest only, balloon, and commercial loans are defined. It concludes with an example yield analysis showing how to calculate rates of return for the equity investor and lender.